What is any membranous bag shaped like a leathern bottle, as the dilated end of a vessel or duct; especially the dilations of the semicircular canals of the ear called?

ampulla — (Biol.) Any membranous bag shaped like a leathern bottle, as the dilated end of a vessel or duct; especially the dilations of the semicircular canals of the ear. (Webster's 1913.)

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